Biological molecules

what is a monomer?

• single unit which join together to form larger molecules

what reaction joins two monomers together?

• condensation reaction

• Molecule of water produced

what reaction breaks a chemical bond between two monomers?

• hydrolysis

• Use of a water molecule

what is the name of monomers in a carbohydrate?

• monosaccharide

What are the different monosaccharides?

• glucose

• Fructose

• Galactose

name the different disaccharides and what they are made of:

• Maltose: condensation of two glucose molecules

• Sucrose: condensation of glucose and fructose molecules

• Lactose: condensation of glucose and galactose molecules

where is the OH group on the isomers of glucose?

• OH above plane on beta (opposite)

• OH below plan on alpha (together)

What sort of bond is created between two monosaccharides?

glycosidic bond

what are polymers of alpha glucose?

• glycogen and starch are formed by condensation of alpha glucose

• Coiled chains

• Insoluble and doesn’t effect water potential

• Large and compact

• Branched and has more ends to be acted on at one given time by enzymes

• Contains 1,6 bonding

• All glucose are the same way up

• No fibres

what is the polymer for beta glucose?

• cellulose formed by condensation of beta glucose

• Forms straight unbranched chains

• Unbranched chains run parallel to one another to form hydrogen bonds

• Contains only 1,4 bonds

• Alternating glucose

• Contains fibres

test for reducing sugar:

• equal parts Benedikt’s solution

• Heat gently for 5 minutes

• Blue to brick red

Test for non reducing sugar:

• Benedikt’s test has to be negative

• Add HCl then heat gently (hydrolyses dissacharides)

• Add sodium hydrogencarbonate and test with pH paper to check it is alkaline

• Add benedikt’s solution and heat

• Blue to brick red

Test for starch:

• iodine test

• Yellow to black

what property of water results in the high temperature required to heat water?

• specific heat capacity of water

• Water molecules form hydrogen bonds

• More energy needed to separate molecules of water

• Requires more energy to heat a mass of water

• Boiling point is higher than expected

• Water is a buffer against sudden changes in temperature

• Good for making aquatic environments temperature-stable

• Good against sudden temperature changes for organisms in terrestrial environments as organisms are made up of water

which property of water results in the large amount of energy required to vapourise water?

• latent heat of vaporisation of water

• Large amount of energy required to evaporate 1 gram of water

• Evaporation is an effective way to cool down as it requires body heat to evaporate water

Which property of water allows it to go up straws?

• cohesion

• Water has large cohesive forces so they can be pulled through tubes like xylem vessels

• Water molecules tend to pull back into a body of water

• Forms surface tension and water surface acts like skin

what is the importance of water?

• makes up organisms

• Is an environment

• Breaks down complex molecules during hydrolysis

• Chemical reactions take place in water

• Major material in photosynthesis

• Solvent for gase

• Provides structural support

• Transparent so aquatic plants can photosynthesise

What is the importance of lipids?

• source of energy

• Waterproofing

• Insulation

• Protection

structure of triglycerides:

• three fatty acid chains combined with three glycerol molecules

• Ester bond formed between chain and glycerol by condensation reaction

• Fatty acid chains have carboxyl group and a hydrocarbon chain (R group)

• Unsaturated means there is a double carbon bond in thee chain, therefore cannot be packed together so closely making them liquid at room temp

Properties of triglycerides:

• high ratio of energy-storing C-H bonds to carbon atoms, excellent source of energy

• Have low mass to energy ratio, good storage molecules

• Large and non-polar, insoluble in water

Structure of phospholipids:

• One phosphate molecule and two fatty acid-glycerol chain

• Phosphate molecule is hydrophilic

• Forms polar molecule

test for lipid

• add sample being tested then ethanol

• Shake tube

• Add water

• Shake tube

• Water forms cloudy white emulsion

What is the monomer of proteins?

amino acids

Structure of amino acid:

• central carbon

• NH2 (amine) group

• COOH (carboxyl group)

• H

• R group

What bond is formed between amino acids?

• peptide bond formed by condensation reaction

• Polypeptides = formation of multiple amino acids by condensation

Structure of proteins:

• primary- formation of polypeptide from sequence of amino acids

• Secondary- forming hydrogen bonds, creating helix 3D shaope

• Tertiary- disulfide bridges, ionic bonds, hydrogen bond results in further folding

• Quaternary- multiple polypeptide chains joining together

what is the test for proteins?

• biuret test, detects peptide bonds

• Add biuret reagent

• Blue to purple colour change

definition of enzyme:

• proteins that act as a catalyst in reactions

use of enzyme:

• speeds up reaction by lowering activation energy without being used up itself

describe the induced fit model of enzymes:

• Substrate binds to active site of enzyme

• Forming enzyme-substrate complex

• Active site changes shape so it is complementary to substrate

• Distorts bonds in substrate

• Reduces activation energy

what are enzyme inhibitors?

• substances that either directly or indirectly interferes with functioning of the active site of an enzyme, reducing its activity

Competitive inhibitors:

• have molecular shape similar o substrate

• Occupies the active site of enzyme

• Competes with substrate for available active site

• reduces rate of reaction, however the reaction will still occur in full

non-competitive inhibitors:

• non-competitive inhibitors attach themselves to enzyme at binding site which is NOT active site

• Inhibitor alters shape on enzyme and so changes shape of alive site

• Substrate can no longer bind to enzyme

Structure of a nuclotide:

• pentose sugar

• Phosphate group

• Nitrogenous base (uracil, thymine, guanine, cytosine, adenine)

• All joined together by condensation reaction

how are polynucleotides made?

• condensation reaction between phosphate group of one nucleotide and pentose sugar of another

• Forms phosphodiester bond

difference between RNA and DNA structure:

• DNA has two strands RNA has one

• DNA contains deoxyribose pentose sugar RNA contains ribose pentose sugar

• DNA has bases T,A,C,G RNA has bases A,U,C,G

• DNA bases form hydrogen bonds RNA doesn’t

how is the DNA stable?

• phosphodiester backbone protects more chemically reactive organic bases within double helix

• Hydrogen bonds between organic bases forms bridges

• Three hydrogen bonds between C-G, so more CG pairings the more stable it is

describe semi-conservative replication:

• enzyme DNA helicase breaks hydrogen bond linking base pairs of DNA

• Double helix unwinds to form two strands

• One strand used as template strand

• Free nucleotides with bases complementary to exposed nucleotide bind

• DNA polymerase joins free nucleotides together by a condensation reaction

• each new DNA molecule contains one of the original DNA strand

what requirements are there for semi conservative repication?

• four types of nucleotide with bases complementary pairs

• Both strands of DNA acting as templates for attachment of nucleotide

• Enzyme DNA polymerase

• Source of chemical energy to drive process

who came up with the idea of semi-conservative replication?

• watson and crick

Structure of ATP:

• adenine base

• Ribose sugar

• Three phosphate groups

How does ATP store energy?

• bond between phosphate groups are unstable and have low activation energy

• When bonds are broken they release a considerable amount of energy

• Usually on the terminal phosphate is removed

• ATP + H₂O —> ADP + P_i + E (energy)

• Hydrolysis reaction as it uses a molecule of water

Describe synthesis of ATP:

• ADP re-forms to ATP by adding phosphate groups

• Catalysed by enzyme ATP synthase

• Condensation reaction as it produces a water molecule

When does synthesis of ATP occur?

• in chlorophyll-containing plant cells during photosynthesis photophosphorylation

• In plant and animal cells during respiration oxidative phosphorylation

• in plant and animal cells when phosphate groups are transferred from donor molecules to ADP substrate-level phosphorylation

roles of ATP:

• metabolic process

• Movement

• Active transport

• Secretion

• Activation of molecules

Why is ATP an immediate energy source?

• good energy donor but not a good long-term storage of energy

• Therefore not stored in large quantities as ADP forms into ATP very quickly